Easy-opening closures

ABSTRACT

The disclosure of this specification relates to an easy-opening closure for a can end wherein the closure is defined by a portion of the end which is completely sheared from the end except at a plurality of positions defining retaining means. The material defining the retaining means is cold worked to be in tension, the material being deformed beyond its elastic limit so that removal of the closure is more readily achieved by applying a force to a pull tab connected to the closure. If the can is required to be hermetically sealed, a sealant is applied to at least the completely sheared regions of the can end.

United States Patent [1 1 Dalli et al.

[ EASY-OPENING CLOSURES [75] Inventors: Alan George Dalli, Warrandyte,

Victoria; Michael Debenham, Frankston, Victoria; Ralph Edward Shackleford, Doncaster East, Victoria, all of Australia [73] Assignee: The Broken Hill Proprietary Company Limited, Melbourne, Australia [22] Filed: Nov. 24, 1970 [2]] Appl. No.: 92,472

[30] Foreign Application Priority Data Nov. 25, l969 Australia 64,291/69 52 us. Cl. 220/54, 220/27 [5 1] Int. Cl B65d 17/20 [58] Field of Search 220/54, 48, 27

[56] References Cited UNITED STATES PATENTS 3,089,609 5/1963 D Andrea 220 54 x [451 Sept. 4, 1973 Primary ExaminerGeorge T. Hall Attorney-Cushman, Darby & Cushman [57] ABSTRACT The disclosure of this specification relates to an easyopening closure for a can end wherein the closure is defined by a portion of the end which is completely sheared from the end except at a plurality of positions defining retaining means. The material defining the retaining means is cold worked to be in tension, the material being deformed beyond its elastic limit so that removal of the closure is more readily achieved by applying a force to a pull tab connected to the closure. If the can is required to be hermetically sealed, a sealant is applied to at least the completely sheared regions of the can end.

11 Claims, 8 Drawing Figures EASY-OPENING CLOSURES This invention relates to easy-opening closures for containers.

All presently known easy-opening closures for can ends are fabricated in aluminium or high aluminium content alloys. The can end is either fabricated wholly from aluminium or aluminium alloy with the closure defined by a score line or other weakening line or comprises a tin plate member to which an insert of aluminium or aluminium alloy, including the closure defined by a weakening line, is secured by crimping and sealing. Due mainly to the high cost of aluminium both of these methods are expensive.

Another disadvantage of aluminium ends is that they cannot be used on large cans (those around three inches in diameter) due to the fact that the end will blow off the can during pasteurizing of the contents or like processes which increase the pressure in the can.

Because of its low cost and high strength steel is an ideal material for can making. Steel is also an ideal material for large can ends as it does not suffer the above disadvantage of aluminium. However all attempts to provide an easy-opening steel can end have so far failed. It has been found impossible to form such closures by means of weakening lines as are used in aluminium ends because the scoring process work-hardens the steel and prevents proper removal of the closure by the usual tearing action.

It is therefore an object of this invention to provide an easy-opening closure construction which can be formed from steel as well as from other metals and materials.

In one form the invention provides an easy-opening closure for a container member comprising a portion which is completely sheared from the member except at a plurality of locations which define retaining means, said retaining means being capable of being readily broken to remove the portion to define an opening.

Where the container must be completely sealed against say the escape of gases, the closure also includes a seal covering at least the completely sheared parts of the portion.

More particularly the invention provides an easyopening closure for a container member, such as a can end, wherein the closure is defined by a portion of the end which is completely sheared from the container member except at a plurality of positions defining retaining means, the material defining the retaining means being in tension and acting to retain the closure in a plane which is adjacent and generally parallel to the plane of the container member in the region of the closure member, said retaining portions being formed so as to be capable of being readily broken by application of a predetermined force to a pull tab or like member adapted to be connected to the closure, and seal means covering at least the completely sheared regions of the container member.

In a particularly preferred form, as applied to can ends of relatively large diameter which are subject to pressure doming, the shearing of the material is performed so that the edges of the closure and the container member are at a negative acute angle to the outer face of the container member. Thus the closure is generally'wedge-shaped so that when doming occurs the closure is allowed to move towards the plane of the container portion and the retaining means are not further stressed.

For such can ends it is also preferred that at least one retaining means is provided in the region of the closure which is closest to the centre of the end and this retaining means is not sheared through at the outer surface of the end but at least some of the other retaining means are so sheared.

The invention also provides a method of making an easy-opening closure for a container member comprising completely shearing a portion from the container member except at a plurality of locations which define retaining means, said retaining means being formed to be in tension to retain the closure in a plane which is closely adjacent and generally parallel to the plane of the container member in the region of the closure.

Where the container member is formed from metal, the retaining means are cold worked so that they are in tension.

For large can ends which are subject to pressure doming the closure is preferably sheared so as to be wedge-shaped as defined above.

An embodiment of the invention, which may be preferred, will now be described with reference to the ac-- companying drawing inwhich:

FIG. 1 is a plan view of a can end incorporating a easy-opening closure embodying the invention;

FIG. 2 is a transverse sectional elevation taken along line 2-2 of the end shown in FIG. 1;

FIG. 3 is a fragmentary plan view of a further can end embodying the invention;

FIG. 4 is a transverse sectional elevation along line 44 of the end of FIG. 3;

FIG. Sis a fragmentary plan view of another can end embodying the invention;

FIG. 6 is a transverse sectional elevation taken along line 6- -6 of FIG. 5;

FIG. 7 is an enlarged fragmentary plan view of the can end of FIG. 5 showing in more detail the easyopening closure, and

FIG. 8 is a fragmentary sectional elevation taken along line 8-8 of FIG. 7.

The container end will be describedas made from coated steel (e.g., tin plate or tin free steels) since this illustrates one of the distinct advantages of the invention; the fact that easy-opening closures can be made in a steel container member using the invention. However, it should be understood that the invention is equally applicable to other suitable metals and even to suitable plastics materials.

FIGS. 1 and 2 show a can end 1, formed into the configuration shown by means of a suitable die, from a flat circular sheet of tin plate. At an off-centre position, an easy-opening closure 2 embodying the present invention is formed.

The closure 2 comprises an area of the end 1 which is entirely sheared through except at selected locations around the periphery of the closure 2 where the metal is cold worked so that these retaining means incorporate residual stresses whichkeep the retaining portions in tension. The retaining portions and their formation will be described in detail below. i

To prevent loss of gas or contents and contamination of the contents of the can through the sheared through portions defining the closure a suitable sealant S (FIG. 2) is applied to the inside face of the end in the region of the closure. Applicant has found that a sealant marketed by W.R. Grace Australia Ltd. under the general name Organosol is suitable. Alternatively a vinyl resin or cellulose sealant may be used. Many other commerically available sealants would also be suitable.

The sealant used should be inert to and not taste the contents of the container and if the container is used to package materials including gases, such as soft drinks, the sealant may have to be modified to prevent permeation of the gas. One such modification comprises mixing microscopic platelets of cellulose, or other material if cellulose is dissolved by the sealant, in the sealant compound. These platelets overlap each other to form layers of impermeable cellulose.

The configuration of closure 2 has been designed to have the shape of a perfect weir but this is only a matter which affects the pouring characteristics of the opening in use and thus does not form an essential part of the invention.

At a position in the closure which is closest to the centre of the can end, the closure is fitted with a pull tab 3. In this embodiment the pull tab is formed from wire and has an inverted frusto-conical end 4 and a flange member adjacent the end 4. The fitting of the tab 3 is achieved by forming an integral cylindrical pocket (not shown), having a generally hemispherical end, in the closure 2, inserting the pull tab end 4 in the pocket and axially deforming same. Since the flange member 5 prevents the material defining the pocket deforming past the flange, it deforms generally radially inwardly to tightly grip the end 4 as shown in FIG. 2.

The above isfound to be a most satisfactory pull tab .arrangement since it functions well and does not suffer from the scrap loss problem associated with sheet metal pull tabs. The arrangement is also advantageous in that it does not include a rivet which passes through the end. However, since the easy-opening closure 2 is unaffected by the pull tab arrangement used it should be understood that other pull tabs, including known arrangements can be used. The only requirements of the pull tab are that it be capable of withstanding the forces associated with the removal of the closure and that it be convenient to grip.

The embodiment shown in FIGS. 3 and 4 is identical to the above except that a recess R is formed in the can end around the end of the pull tab to allow this to lie flush against the end whilst permitting a finger to engage under the pull tab. The connection to the can end is also slightly different in that a rivet 10 is used instead of an integral part of the pull tab.

Many different forms of wire pull tab other than those shown may be used. For example the wire may be shaped in the form of a partial or complete ring and having part of the ring bent out of the plane of the rest of the tab to facilitate gripping. Furthermore the pull tab may be fitted to the closure by a rivet engaging a cylindrical socket in the closure as an interference fit.

The embodiment shown in FIGS. 5 to 8 represents a construction which is more commercially acceptable than the two preceding embodiments. However, it is in essence the same except that the shape of the closure 2 is teardrop shaped and the pull tab 3 comprises a sheet metal loop which is spot welded at X to the closure 2. An arcuate recess R is formed in the end 1 adjacent the pull tab 3 to facilitate the engagement of a finger for the removal operation.

Referring now more particularly to FIGS. 7 and 8, the closure 2 is formed by a punching die which is preferably incorporated in the die which forms the can end 1 from the circular sheet. In the preferred form shown in FIGS. 5 and 6 of the drawing the retaining means comprise five identical portions 7 arranged as shown to retain the main part of the closure 2 and two portions 8 arranged at the end of the closure which is closest to the centre of the end. The retaining portions 7 are slightly sheared through at the outer surface of the end and include notches formed in the direction of the line along which the material is sheared at the inner face of the end to assist in the tearing of the portions 7 when the closure is opened. However, the retaining portions 8 are not sheared through at all and do not include notches. The reason for this is that the retaining portions need to be stronger in this region to prevent undesired opening of the closure due to the concentration of strains at this end of the closure when the end is subject to pressure from inside the container. The additional strength in these retaining portions does not substantially affect the opening characteristics of the closure since all of the initial leverage applied to the pull tab is concentrated in this region of the closure. The cold working of the retaining portions 7 and 8 which takes place during the die operation is such that the retaining portions 7 and 8 are in tension. This means that these portions 7 and 8 act to pull the closure back into the opening to therefore make the gap between closure and end as narrow as possible. The cold working is also such that the metal defining the retaining portions 7 and 8 is deformed beyond its elastic limit so that easy removal of the closure is facilitated.

The width of the retaining portions 7 and 8 and the extent to which portions 7 are sheared through and notched is selected .to provide a suitable opening force whilst preventing the breaking of the retaining portions during the packing processes and nonnal handling. It is also preferred that the retaining portions 7 be formed so that they are at about 45 to the rolling direction of the steel from which the steel end is formed and that the steel temper be selected to provide a suitable pullout strength of the closure 2.

It is also preferred that the closure 2 be sheared out so that the edges of the opening and the closure are inclined at between 45 to 89 (45 being most preferred and shown in FIG. 8) to the outer face of the end so that the closure 2 is wedge shaped at its edges in the direction of the outer face. With this form of shearing, doming of the end due to increasing container pressures, which occur in packaging processes and normal handling, the closure 2 is allowed to be drawn into the opening be the retaining portions 7 and 8 and so these retainers are not further stressed as would be the case with 90 shearing. Furthermore the gap between the end and closure is reduced rather than increased by the doming and so rupture or peaking of the sealant, which has no strength of its own, does not occur.

It will of course be appreciated that doming in can ends of relatively small diameter is negligible so in such ends wedging of the closure is not required. Thus, the invention in its broader aspect is not limitedto this feature. Similarly the retaining portions 8 may be reduced to one or more and it may be possible to sever and/or notch these in a manner similar to portions 7.

It will be noted that the embodiments of FIGS. 1 to 4 have only 4 retaining portions 7 and two retaining portions 8 (not visible). Thus it will be appreciated that the arrangement and number of the retaining portions will be selected according to the shape of the opening and its position in the can end. For example it may be possible to reduce the number of portions 8 by moving the opening further away from the centre of the end to a position where the strains are not so great. It would also be possible to form larger openings in the end so that substantially all of the end is removable.

If desired the closure 2 may be located in a depressed area of approximately the same shape as the closure. The depth of the depression need only be small, say about 0.015 inch, and the spacing between the edge of the closure and the edge of the depressed area is of similar dimensions. With this arrangement the raw edges of the can end defining the opening are directed inwardly of the end so that when a beverage is drunk directly from the can, injury to the consumers lips is prevented.

In another embodiment not shown in the drawings, the closure 2 is left connected to the end 1, for example, between the portions 8, so that the closure remains connected to the end on opening thereof. For such an arrangement the pull tab is connected to the closure at a position adjacent the periphery of the end and the tab overlies the closure. This embodiment has two advantages: (l the closure remains connected to the end so reducing the litter problem associated with known easy-opening ends, and (2) th portion connecting the closure to the end is near the centre of the end where strength is required to prevent rupture during processing and handling.

We claim:

I. An easy-opening closure in a steel container member, wherein the closure is defined by a portion of the container member which is completely sheared from the container member except at a plurality of positions defining retaining means, said container member being sheared at an acute angle to the outer face of the container member to produce a closure which is larger than the opening in the container member, said closure engaging the opening to put the material defining the retaining means in tension to retain the closure in a plane which is adjacent and generally parallel to but below the plane of the container member in the region of the closure member, said retaining portions being formed so as to be capable of being readily broken by application of a predetermined force to a pull tab member connected to the closure, and seal means covering at least the completely sheared regions of the container member if required by the purpose the closure is to serve.

2. An easy-opening closure as claimed in claim 1, wherein the steel defining said retaining means is cold worked metal which is beyond its elastic limit.

3. An easy-opening closure as claimed in claim 2, wherein the acute angle is of the order of 45.

4. An easyopening closure as claimed in claim 3, wherein the container member is a can end and the closure is formed with one part adjacent the center of said can end, there being at least one retaining means adjacent this part and a plurality of retaining means spaced around the closure, said plurality being partially sheared through at one face of the can end and being notched in the direction of shearing at the opposite face, said at least one retaining means being characterized by the absence of partial shearing and notching.

5. An easy-opening closure in a metal can end, said closure being defined by a portion of the can end which is completely sheared at an acute angle to the outer face of the can end from the can end except at a plurality of positions defining retaining means, said closure being larger than the opening in the can end, said closure engaging said opening to put the material defining the retaining means in tension to retain the closure in a plane which is adjacent and generally parallel to but below the plane of the can end in the region of the closure member, pull-tab member means connected to the closure to facilitate opening same, said retaining means being capable of being readily broken by application of a predetermined force to said pull-tab member means, and seal means covering at least the completely shearedregions of the can end if required by the purpose the closure is to serve.

6. The closure of claim 5 wherein said acute angle is from 45 to 89.

7. The closure of claim 6 wherein said angle is about 45.

8. Closure of claim 7 wherein said can end and said closure are of steel.

9. Closure of claim 8 wherein the steel defining said retaining means is cold worked steel which is beyond its elastic limit.

10. Container of claim 9, wherein said closure is generally wedge-shaped in cross-section.

11. Closure of claim 10 wherein a portion of the closure is adjacent the center of said can end, there being at least one retaining means adjacent this portion and a plurality of retaining means spaced around the closure, said plurality of retaining means being partially sheared through at one face of the can end and being notched in the direction of shearing at the opposite face of the can end, and the said at least one retaining means being characterized by the absenceof partial shearing and notching. 

1. An easy-opening closure in a metal container member, wherein the closure is defined by a portion of the container member which is completely sheared from the container member except at a plurality of positions defining retaining means, said container member being sheared at an acute angle to the outer face of the container member to produce a closure which is larger than the opening in the container member, said closure engaging the opening to put the material defining the retaining means in tension to retain the closure in a plane which is adjacent and generally parallel to but below the plane of the container member in the region of the closure member, said retaining portions being formed so as to be capable of being readily broken by application of a predetermined force to a pull tab member connected to the closure, and seal means covering at least the completely sheared regions of the container member if required by the purpose the closure is to serve.
 2. An easy-opening closure as claimed in claim 1, wherein the metal defining said retaining means is cold worked metal which is beyond its elastic limit.
 3. An easy-opening closure as claimed in claim 2, wherein the acute angle is of the order of 45*.
 4. An easy-opening closure as claimed in claim 1, wherein the container member is a can end and the closure is formed with one part adjacent the center of said can end, there being at least one retaining means adjacent this part and a plurality of retaining means spaced around the closure, said plurality being partially sheared through at one face of the can end and being notched in the direction of shearing at the opposite face, said at least one retaining means being characterized by the absence of partial shearing and notching.
 5. An easy-opening closure in a metal can end, said closure being defined by a portion of the can end which is completely sheared at an acute angle to the outer face of the can end from the can end except at a plurality of positions defining retaining means, said closure being larger than the opening in the can end, said closure engaging said opening to put the material defining the retaining means in tension to retain the closure in a plane which is adjacent and generally parallel to but below the plane of the can end in the region of the closure member, pull-tab member means connected to the closure to facilitate opening same, said retaining means being capable of being readily broken by application of a predetermined force to said pull-tab member means, and seal means covering at least the completely sheared regions of the can end if required by the purpose the closure is to serve.
 6. The closure of claim 5 wherein said acute angle is from 45* to 89*.
 7. The closure of claim 6 wherein said angle is about 45*.
 8. Closure of claim 5 wherein said can end and said closure are of steel.
 9. Closure of claim 8 wherein the steel defining said retaining means is cold worked steel which is beyond its elastic limit.
 10. Container of claim 8, wherein said closure is generally wedge-shaped in cross-section.
 11. Closure of claim 8 wherein a portion of the closure is adjacent the center of said can end, there being at least one retaining means adjacent this portion and a plurality of retaining means spaced around the closure, said plurality of retaining means being partially sheared through at one face of the can end and being notched in the direction of shearing at the opposite face of the can end, and the said at least one retaining means being characterized by the absence of partial shearing and notching. 